1. Field of the Invention
The present invention relates to a near-field light generating element for use in heat-assisted magnetic recording where a recording medium is irradiated with near-field light to lower the coercivity of the recording medium for data writing, a method of manufacturing the same, and a heat-assisted magnetic recording head that includes the near-field light generating element.
2. Description of the Related Art
Recently, magnetic recording devices such as magnetic disk drives have been improved in recording density, and thin-film magnetic heads and recording media of improved performance have been demanded accordingly. Among the thin-film magnetic heads, a composite thin-film magnetic head has been used widely. The composite thin-film magnetic head has such a structure that a read head including a magnetoresistive element (hereinafter, also referred to as MR element) for reading and a write head including an induction-type electromagnetic transducer for writing are stacked on a substrate. In a magnetic disk drive, the thin-film magnetic head is mounted on a slider that flies slightly above the surface of the magnetic recording medium.
To increase the recording density of a magnetic recording device, it is effective to make the magnetic fine particles of the recording medium smaller. Making the magnetic fine particles smaller, however, causes the problem that the magnetic fine particles drop in the thermal stability of magnetization. To solve this problem, it is effective to increase the anisotropic energy of the magnetic fine particles. However, increasing the anisotropic energy of the magnetic fine particles leads to an increase in coercivity of the recording medium, and this makes it difficult to perform data writing with existing magnetic heads.
To solve the foregoing problems, there has been proposed a technique so-called heat-assisted magnetic recording. This technique uses a recording medium having high coercivity. When writing data, a magnetic field and heat are simultaneously applied to the area of the recording medium where to write data, so that the area rises in temperature and drops in coercivity for data writing. The area where data is written subsequently falls in temperature and rises in coercivity to increase the thermal stability of magnetization. Hereinafter, a magnetic head for use in heat-assisted magnetic recording will be referred to as a heat-assisted magnetic recording head.
In heat-assisted magnetic recording, near-field light is typically used as a means for applying heat to the recording medium. A known method for generating near-field light is to apply laser light to a plasmon antenna, which is a small piece of metal, as described in U.S. Patent Application Publication No. 2008/0055762 A1, for example. The laser light applied to the plasmon antenna excites surface plasmons on the plasmon antenna, and near-field light is generated based on the surface plasmons. The near-field light generated by the plasmon antenna exists only within an area smaller than the diffraction limit of light. Irradiating the recording medium with the near-field light makes it possible to heat only a small area of the recording medium.
A possible configuration of the heat-assisted magnetic recording head is such that, in a medium facing surface that faces the recording medium, an end face of a magnetic pole that produces a write magnetic field is located on the trailing side relative to a front end face of a near-field light generating element which is a piece of metal that generates near-field light. The trailing side relative to a reference position refers to the side closer to the air outflow end of the slider relative to the reference position. The trailing side typically falls on the side farther from the top surface of the substrate relative to the reference position. When the above-described configuration is employed, the front end face of the near-field light generating element preferably has a pointed top end so that a near-field light generating part is formed near the top end of the front end face.
In order to increase the recording density of the magnetic recording device, it is preferred that the near-field light have a smaller spot diameter. When the foregoing configuration is employed, it is effective to form the top end of the front end face of the near-field light generating element into a more sharply pointed shape so as to produce near-field light having a small spot diameter and sufficient intensity.
As a method for forming the near-field light generating element having the front end face with a pointed top end, a metal film to make the near-field light generating element may be etched by using an etching mask of photoresist. The formation of the near-field light generating element by such a method, however, has the problem that the top end of the front end face will become rounded, and it is thus difficult to form a near-field light generating element having a front end face with a sharply pointed top end.